Windscreen wiper drive

ABSTRACT

In a windshield wiper drive mechanism, having a pivotably supported drive shaft, a drive rocker ( 10 ) solidly connected to it, a coupling rocker ( 14 ) that is connected to the drive rocker by a drive joint ( 16 ), a support rocker ( 18 ) that is connected to the coupling rocker ( 14 ) by a support joint ( 20 ) and is supported by a blind joint ( 22 ), a windshield wiper arm ( 26 ), which is connected to the coupling rocker by a joint ( 28 ), a contact-pressure spring ( 30 ) that acts upon the windshield wiper arm relative to the coupling rocker, and a compensation joint ( 24 ) that is disposed on one of the rockers, the object is for the tilting moments generated by the contact-pressure spring to be reduced. To that end, a compensation spring ( 34 ) is provided on the compensation joint.

BACKGROUND OF THE INVENTION

The invention relates to a windshield wiper drive mechanism, having apivotably supported drive shaft, a drive rocker solidly connected to it,a coupling rocker that is connected to the drive rocker by a drivejoint, a support rocker that is connected to the coupling rocker by asupport joint and is supported by a blind joint, a windshield wiper arm,which is connected to the coupling rocker by a joint, a contact-pressurespring that acts upon the windshield wiper arm relative to the couplingrocker, and a compensation joint that is disposed on one of the rockers.

One such windshield wiper drive mechanism is known from European PatentDisclosure EP-A 0 182 123. It serves to move a windshield wiper blade,secured to the windshield wiper arm, with a reciprocating motion over awindshield to be cleaned. To prevent twisting from occurring in themechanism, based on a four-bar mechanism, that comprises the driverocker, coupling rocker and support rocker, the compensation joint isprovided, which is disposed on the coupling rocker and divides it intotwo portions movable relative to one another. This disadvantage in thisconstruction is that the contact-pressure spring exerts a tilting momenton the coupling rocker, and this leads to increased stresses on thevarious bearings.

The object of the invention is thus to refine a windshield wiper drivemechanism of the type defined at the outset such that the tilting momentgenerated by the contact-pressure spring does not impair the operationof the windshield wiper drive mechanism.

SUMMARY OF THE INVENTION

The windshield wiper drive mechanism has the advantage that acompensation spring compensates entirely or at least in part for thetilting moment generated by the contact-pressure spring, so that thebearings of the coupling rocker experience less stress. Thus they can bemade smaller, and non-jerking travel of the entire windshield wiperdrive mechanism is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described below with reference to various embodimentsthat are shown in the accompanying drawings. Shown in the drawings are:

FIG. 1, in a schematic elevation view, a windshield wiper drivemechanism in a first embodiment of the invention;

FIG. 2, in a perspective elevation view, the drive rocker, supportrocker and coupling rocker of the windshield wiper drive mechanism ofFIG. 1;

FIG. 3, in a schematic elevation view, a windshield wiper drivemechanism in a second embodiment of the invention;

FIG. 4, in a perspective elevation view, the drive rocker, supportrocker and coupling rocker of the windshield wiper drive mechanism ofFIG. 3; and

FIG. 5, in a schematic elevation view, a windshield wiper drivemechanism in a third embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 schematically shows a windshield wiper drive mechanism in a firstembodiment. It includes a drive rocker 10, which is supported, solidlysecure to the vehicle, in a pivot joint 12 for the drive rockers. Thedrive rocker 10 can be set to reciprocation by a windshield wiper motor(not shown).

A coupling rocker 14 is connected to the drive rocker 10 by means of adrive joint 16. The drive joint 16 is embodied here as a pivot joint.Connected to the coupling rocker 14 is a support rocker 18 by means of asupport joint 20, which is embodied here as a ball joint. The supportrocker 18 is supported in a manner solidly connected to the vehicle by ablind joint 22, embodied here as a pivot joint. Between the supportjoint 20 and the blind joint 22, the support rocker 18 is provided witha compensation joint 24, whose pivot axis is defined approximatelyperpendicular to the pivot axis defined by the blind joint 22. Thecompensation joint 24 makes it possible to pivot the support joint 20 ina plane that is defined by the pivot axis of the blind joint 22 and bythe support joint 20.

Connected to the coupling rocker 14, in a manner known per se, is awindshield wiper arm 26, and a windshield wiper arm pivot joint 28 and acontact-pressure spring 30 are provided, so that a windshield wiperblade 32 mounted on the windshield wiper arm 26 is urged toward a windowto be cleaned.

A compensation spring 34 which is embodied as a tension spring actsbetween the two portions of the support rocker, which are located on oneside and the other of the compensation joint 24. The compensation springis disposed and dimensioned such that it compensates for the tiltingmoment that is exerted on the drive joint 16 as a result of thecompensation spring and the windshield wiper blade 32 braced against thewindow; the compensation spring thus generates a force acting upon thesupport joint toward the window.

As can be seen in FIG. 2, the compensation spring is integrated with thesupport rocker. The force exerted by it on the support joint can beadjusted by means of the spacing of the line of action of thecompensation spring from the axis of the compensation joint 24 and bymeans of the spring force.

In FIGS. 3 and 4, a windshield wiper drive mechanism in a secondembodiment is shown. For the components known from the first embodiment,the same reference numerals are used, and the reader is referred to theexplanations above.

In the second embodiment as well, a five-bar mechanism is involved.Compared to the first embodiment, however, the disposition of the jointsfor the drive rocker and the support rocker are transposed; that is, thesupport joint 20 is embodied as a pivot joint, while the drive joint 16is now a ball joint. Also the drive rocker is now provided with thecompensation joint 24 and the compensation spring 34.

In FIG. 5, a windshield wiper drive mechanism in a third embodiment isshown. Once again, for the components known from the above embodiments,the same reference numerals are used, and reference is made to the aboveexplanations.

Unlike the first two embodiments, in the third embodiment the couplingrocker is provided with the compensation joint 24 and the compensationspring 34, so that the support joint is relieved directly of the tiltingmoment that is generated by the contact-pressure spring.

List of Reference Numerals 10: Drive rocker 12: Pivot joint for driverockers 14: Coupling rocker 16: Drive joint 18: Support rocker 20:Support joint 22: Blind joint 24: Compensation joint 26: Windshieldwiper arm 28: Windshield wiper arm pivot joint 30: Contact-pressurespring 32: Windshield wiper blade 34: Compensation spring

What is claimed is:
 1. A windshield wiper drive mechanism, having apivotably supported drive shaft, a drive rocker (10) solidly connectedto it, a coupling rocker (14) that is connected to the drive rocker by adrive joint (16), a support rocker (18) that is connected to thecoupling rocker (14) by a support joint (20) and is supported by a blindjoint (22), a windshield wiper arm (26), which is connected to thecoupling rocker by a joint (28), a contact-pressure spring (30) thatacts upon the windshield wiper arm relative to the coupling rocker, anda compensation joint (24) that is disposed on one of the rockers,characterized in that a compensation spring (34) is provided on thecompensation joint.
 2. The windshield wiper drive mechanism of claim 1,characterized in that the drive joint (16) is a ball joint; that theblind joint (22) and the support joint (20) are each a pivot joint; andthat the compensation joint (24) and the compensation spring (34) aremounted on the coupling rocker (14).
 3. The windshield wiper drivemechanism of claim 1, characterized in that the drive joint (16) is aball joint; that the blind joint (22) and the support joint (20) are apivot joint; and that the compensation joint (24) and the compensationspring (34) are mounted on the drive rocker (10).
 4. The windshieldwiper drive mechanism of claim 1, characterized in that the drive joint(16) and the blind joint (22) are a pivot joint; that the support joint(20) is a ball joint; and that the compensation joint (24) and thecompensation spring (34) are mounted on the support rocker (18).
 5. Thewindshield wiper drive mechanism of claim 1, characterized in that thecompensation spring (34) is a tension spring.